Sheesh, a lot of people seem to have a bunch of excess cash that they need to send to me - talk about a gold brick! Between sticking any old USB WiFi dongle in to get NTP, to the cron script that adjusts for measured drift where WiFi may not be available, if that isn't good enough, you're using the wrong kind of computer.
Something that I just noticed is that some old smart phones I have still remain synched with the time service, even though they are no longer under a current service contract. They do have GPS, so that may be where they're getting the time signal from, but I wonder if a USB cell dongle without a current service contract can track time via the service. It may work because even out-of-contract phones can be used to call 911 (or whatever the emergency number may be in your area) and so they can be tracked at least by cell tower triangulation. Time synching may be necessary for that to work, so that's why it continues past end-of-contract. I don't have any cell dongles to test this theory, but maybe someone else does.
The best things in life aren't things ... but, a Pi comes pretty darned close!
"Education is not the filling of a pail, but the lighting of a fire." -- W.B. Yeats
In theory, theory & practice are the same - in practice, they aren't!!!